Separation system and method

ABSTRACT

One exemplary embodiment can be a separation system. The separation system can include an adsorption zone, a rotary valve, a transition zone, and one or more pipes. Usually, the transition zone includes one or more lines communicating the rotary valve with the adsorption zone. The rotary valve alternatively may distribute an input of a feed or a desorbent to the adsorption zone or alternatively can receive an output of a raffinate or an extract from the adsorption zone in a line, and a remnant may remain in the line from a previous input or output. One or more pipes outside the transition zone communicating with the rotary valve can form at least one pipe volume receiving an input for dislodging a remnant or for receiving a remnant from the line. The remnant may be different from the input or output.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Division of prior copending application Ser. No.12/412,482 which was filed Mar. 27, 2009, the contents of which areincorporated herein by reference thereto.

FIELD OF THE INVENTION

This invention generally relates to a separation system for separating adesired component from one or more other components in a stream.

DESCRIPTION OF THE RELATED ART

Adsorptive separation can be used to purify a hydrocarbon stream byselecting a single compound from one or more other compounds in astream. Generally, it is desirable to obtain the highest possible purityof the adsorbed compound. As a consequence, usually minimizingcontamination of the product is preferable.

In technology such as a simulated moving bed, typically two streams areprovided to the bed, namely a feed and a desorbent, and two streams arewithdrawn from the bed, namely a raffinate and an extract. Impuritiescan occur when supplying and removing these various streams to the bedbecause often the same lines are utilized to provide the feed anddesorbent as well as withdrawing the raffinate and extract. As aconsequence, the next stream in the series can contain remnants from anearlier stream, and thus degrade operations and/or product purity. As aconsequence, it would be desirable to provide an adsorptive separationsystem that minimizes the contaminants and enhances operations andproduct purity.

SUMMARY OF THE INVENTION

One exemplary embodiment can be a separation system. The separationsystem can include an adsorption zone, a rotary valve, a transitionzone, and one or more pipes. Usually, the transition zone includes oneor more lines communicating the rotary valve with the adsorption zone.The rotary valve alternatively may distribute an input of a feed or adesorbent to the adsorption zone, or alternatively can receive an outputof a raffinate or an extract from the adsorption zone in a line, and aremnant may remain in the line from a previous input or output. One ormore pipes outside the transition zone communicating with the rotaryvalve can form at least one pipe volume receiving an input fordislodging a remnant or for receiving a remnant from the line. Theremnant may be different from the input or output.

Another exemplary embodiment can be a separation system for separating adesired component from one or more other components in a stream. Theseparation system can include an adsorption zone, a rotary valve, and atransition zone. The transition zone can include a plurality of linescommunicating the rotary valve with the adsorption zone. The pluralityof lines may be segregated into pairs with one line adapted to bring aninput to the adsorption zone, and the other line adapted to receive anoutput from the adsorption zone, and each line of the pair contains arespective check valve.

A further exemplary embodiment may include a method of minimizingcross-contamination of fluids in a simulated moving bed. The method caninclude filling a replacement volume on one side of a valvecorresponding to a volume in a line on the other side of the valve toeither dislodge a remnant in the line from a previous input, or receivea remnant in the line from a previous output. Generally, the previousinput or output is different from the current input or output.

As disclosed herein, the embodiments can provide a system and method forminimizing contamination of various streams sent and received from anadsorptive bed. Particularly, the embodiments disclosed herein areparticularly applicable to a simulated moving bed technology wherecontamination of the various streams can be avoided. As an example,avoiding contamination can improve the extraction of the desiredcomponent from a feed as well as minimizing contamination of a finalproduct. Providing at least one pipe volume acting as a receptacle foran output of a raffinate or an extract, or an input that can displace aremnant of a feed or desorbent in a line can facilitate the purity ofthe streams provided to the adsorptive zone and/or enhance the purity ofthe output, such as a raffinate and an extract. Hence, the embodimentsdisclosed herein can provide a higher purity product and higher recoveryof the product.

DEFINITIONS

As used herein, the term “stream” can be a stream including varioushydrocarbon molecules, such as straight-chain, branched, or cyclicalkanes, alkenes, alkadienes, and alkynes, and optionally othersubstances, such as gases, e.g., hydrogen, or impurities, such as heavymetals, and sulfur and nitrogen compounds. The stream can also includearomatic and non-aromatic hydrocarbons. Moreover, the hydrocarbonmolecules may be abbreviated C1, C2, C3 . . . Cn where “n” representsthe number of carbon atoms in the one or more hydrocarbon molecules.

As used herein, the term “zone” can refer to an area including one ormore equipment items and/or one or more sub-zones. Equipment items caninclude one or more reactors or reactor vessels, heaters, exchangers,pipes, pumps, compressors, and controllers. Additionally, an equipmentitem, such as a reactor, dryer, or vessel, can further include one ormore zones or sub-zones.

As depicted, process flow lines in the figures can be referred to aslines, pipes or streams. Particularly, a line or a pipe can contain oneor more streams, and one or more streams can be contained by a line or apipe. To facilitate understanding, a line may refer to a conduit in atransition zone between an adsorption zone and rotary valve, and a pipemay refer to a conduit outside the transition zone and/or rotary valve.

As used herein, the term “pipe volume” can mean a portion of a pipe thatmay have a larger diameter than surrounding portions so as to contain acorresponding volume in a line from a transition zone.

As used herein, the term “adsorption” can include adsorption and/orabsorption.

As used herein, the term “adsorbent” can include an adsorbent and/or anabsorbent, and relates, but is not limited to, adsorption, and/orabsorption.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of an exemplary separation system.

DETAILED DESCRIPTION

The embodiments disclosed herein can be utilized in a variety ofadsorptive separation processes. As an example, the embodiments can beutilized for separating para-xylene from a mixture of C8 aromaticisomers, meta-xylene from a mixture of C8 aromatic isomers, linearparaffins from branched and cyclic hydrocarbons, olefins from paraffins,para-cresol or meta-cresol from other cresol isomers, para-cymene ormeta-cymene from other cymene isomers, and fructose from mixed sugars.Other applications can include extracting, independently, one or more ofthe following compounds: monomethyl paraffins, 2,6-dimethyl naphthalene,ethylbenzene, 1-butene, ethyl toluenes, toluidines, terpenes, chloro andnitro aromatics, alpha and beta naphthols, alkyl naphthalenes, alphaolefins, and tall oil, from one or more other compounds. Thus, theembodiments disclosed herein can be used to separate one hydrocarbonfrom one or more other hydrocarbons.

Typically, the adsorbents can be porous solids. Generally, when theadsorbent is adsorbed in a liquid mixture, the pores fill with liquid,but the equilibrium of distribution of components inside the pores isdifferent from the distribution in the surrounding bulk liquid. Theadsorbent can be selective for any component that may be moreconcentrated inside the pores than surrounding the bulk liquid.

Generally, adsorbents can be classified as polar and nonpolar. A polaror hydrophilic adsorbent can include at least one of a silica gel, anactivated aluminum, a silica alumina adsorbent, a molecular sieve and aclay. One exemplary molecular sieve can be a synthetic crystallinezeolite. A wide variety of selectivities can be obtained in suchmolecular sieves by varying a silica-aluminum ratio, a crystalstructure, and cations in the crystal lattice. A nonpolar adsorbent caninclude at least one of an activated carbon and a coal-derived carbon.Generally, a polar adsorbent is used when the components to be removedare more polar than the bulk process liquid, while a nonpolar adsorbentis used when the target components are less polar.

The embodiments disclosed herein can be utilized with a simulated movingbed using a rotary valve. Typically, a rotary valve switches in steps tofacilitate transfer of fluids to and from the adsorption beds. Ashereinafter described, valves in a region outside the transition zonecan be synchronized with the rotary valve's movements. Such exemplarysimulated moving beds are disclosed in, e.g., U.S. Pat. No. 3,392,113,U.S. Pat. No. 3,617,504, U.S. Pat. No. 4,434,051, and U.S. Pat. No.6,407,301 B1.

In these simulated beds, typically a feed and a desorbent are applied atdifferent locations in the bed along with withdrawals of an extract anda raffinate. A circulating adsorbent chamber fluid can simulate a movingbed by changing the composition of the liquid surrounding the adsorbent.Changing the liquid can cause different chemical species to be adsorbedon, and desorbed from, the adsorbent. As an example, initially applyingthe feed to the adsorbent can result in the desired compound or extractto be adsorbed on the adsorbent, and subsequently applying the desorbentcan result in the extract being desorbed and the desorbent beingadsorbed. In such a manner, various materials may be extracted from afeed.

Referring to FIG. 1, an exemplary separation system 100 is depicted. Theseparation system 100 can include an adsorption zone 200, a rotary valve300, a transition zone 400, and a region 600. The adsorption zone 200can include an adsorber 210, and a line 220 that can allow thecirculation of an adsorbent chamber fluid to simulate a moving bed.Generally, the adsorber 210 can include four beds, namely a first bed230, a second bed 240, a third bed 250, and a fourth bed 260. Althoughfour beds are disclosed, it should be understood that any number of bedscan be used, such as 8, 12, 16, 19, 22, 25, or more.

In addition, a rotary valve 300 is depicted. It should be noted that therotary valve 300 is depicted in a schematic form to ease depiction ofthe various stream flows. The rotary valve can be a four-track rotaryvalve, although other rotary valves can be utilized. In addition, itshould be understood that although a rotary valve 300 is depicted, othersuitable devices, such as a multivalve manifold arrangement, may be usedas well.

The transition zone 400 can include one or more lines such as aplurality of lines 404. Generally, the one or more lines 404 can includea first pair of lines 410, a second pair of lines 420, a third pair oflines 430, and a fourth pair of lines 440. Referring to the first pairof lines 410, generally, the first pair of lines 410 can include a firstline 412 having a check valve 414 and a second line 416 having a checkvalve 418. Correspondingly, the second pair of lines 420 can include afirst line 422 having a check valve 424 and a second line 426 having acheck valve 428. In addition, the third pair of lines 430 can have afirst line 432 having a check valve 434 and a second line 436 having acheck valve 438. Moreover, the fourth pair of lines 440 can have a firstline 442 having a check valve 444 and a second line 446 having a checkvalve 448. Generally, the check valves 414, 418, 424, 428, 434, 438,444, and 448 permit fluid in only one direction, namely toward or awayfrom the adsorption zone 200. Although check valves are disclosed, otherunidirectional flow devices may also be used. Particularly, the firstlines 412, 422, 432, and 442, of each of the respective pair of lines410, 420, 430, and 440 can direct fluid in a single direction towardrespective beds 230, 240, 250, and 260. Similarly, the second lines 416,426, 436, and 446 can lead fluid in a single direction away from therespective beds 230, 240, 250, and 260.

The region 600 can include one or more pipes 604 and one or more valves606 outside the rotary valve 300 and/or the transition zone 400. The oneor pipes 604 can include at least one pipe volume 608 corresponding to avolume of one or more lines 404 in the transition zone 400, ashereinafter described. The at least one pipe volume 608 can include afirst pipe volume 610, a second pipe volume 630, a third pipe volume650, and a fourth pipe volume 670. Generally, feed and desorbent streams504 and 508 can be provided through the one or more pipes 604, namely apipe 612, and a pipe 632, and raffinate and extract streams 524 and 528can leave the separation system 100 via a pipe 652 and a pipe 672.Usually, the adsorption zone 200 can receive an input 500 of at leastone of the feed stream 504 and the desorbent stream 508 and provide anoutput 520 of at least one of the raffinate stream 524 and the extractstream 528.

In addition, the one or more valves 606 can control the fluid flowthrough the region 600. A first control valve 614 and a second controlvalve 616 can be throttled to regulate the fluid flow in the first pipevolume 610 and in the pipe 612, and a first control valve 634 and asecond control valve 636 can be throttled to regulate the fluid flow inthe second pipe volume 630 and in the pipe 632. Also, a first controlvalve 654 and a second control valve 656 can be throttled to regulatethe fluid flow in the third pipe volume 650 and in the pipe 652, and afirst control valve 674 and a second control valve 676 can be throttledto regulate the flow in the fourth pipe volume 670 and in the pipe 672.These control valves can be flow control valves or be actionable withother process parameters, such as fluid composition.

In addition to the control valves, other sets 620, 640, 660, and 680 ofvalves can be utilized to control the fluid flow. These sets 620, 640,660, and 680 can be control valves or global valves, and in thisexemplary embodiment they can be global valves. Particularly, a firstset of valves 620 can include a first valve 622 and a second valve 624for regulating the fluid flow in the first pipe volume 610 and the pipe612; a second set of valves 640 can include a first valve 642 and asecond valve 644 for regulating the fluid flow in the second pipe volume630 and the pipe 632; a third set of valves 660 can include a firstvalve 662 and a second valve 664 for regulating the fluid flow in thethird pipe volume 650 and the pipe 652; and the fourth set of valves 680can include a first valve 682 and a second valve 684 for regulating theflow in the fourth pipe volume 670 and the pipe 672.

During steady-state operations, the pipe volumes 610 and 630 are used topreload one of the lines 412, 422, 432, or 442, for the next input 500entering the line. As an example, at the end of the feed cycle, apreload of desorbent is inserted into one of the lines 412, 422, 432, or442 to be pushed into the adsorption zone 200 at the next desorbentcycle.

Particularly, the feed in the pipe 612 and the raffinate in the pipe 632can be provided to the rotary valve 300 and to each of the pair of lines410, 420, 430, and 440, in succession. As a result, the feed, as anexample, can pass through the rotary valve 300 through the first line412 and the check valve 414 to the adsorption bed 230 in the adsorptionzone 200. Previous to the embodiments disclosed herein, the first line412 can contain a remnant from a previous cycle that is not the feed.Generally, it would be preferable to dislodge this remnant to preventits mixing with the feed in the bed 230. Thus, the second control valve616 can be throttled to allow desorbent to fill the first pipe volume610, which initially can contain the feed, and displace feed in thefirst pipe volume 610 to the pipe 612. During this displacement, thesecond valve 624 can be closed and the first valve 622 can be opened.The rate of the fluid flow into the pipe 612 can be regulated to allowthe desorbent to slowly push the feed that is in the first pipe volume610 into the pipe 612. At this point, once the first pipe volume 610fills and the second control valve 616 can be closed, and the feed maypass through the first line 412.

Near the end of the feed cycle, the feed can pass through the first pipevolume 610 by closing the first valve 622 and opening the second valve624. This pushes the desorbent in the first pipe volume 610 through thesecond valve 624 and into the first line 412 pushing the desorbent aheadof the feed stream 504. So, at the beginning of the desorbent cycle, thedesorbent can push the preloaded desorbent, instead of a feed remnant,in the first line 412 into the first bed 230. Thus, feed contaminationof the desorbent cycle can be minimized.

Similarly, the desorbent stream 508 can pass through the pipe 632 andinto the rotary valve 300. Subsequently, the desorbent can pass into thefirst line 422, pass through the one-way check valve 424, and into thesecond bed 240. During the cycle, the feed can pass through the secondcontrol valve 636 and fill the second pipe volume 630 with a feed. Whilethe second pipe volume 630 is being filled, desorbent can be displacedand pushed into the pipe 632. The first control valve 634 can controlthe normal flow of desorbent in the pipe 632. Once the second pipevolume 630 is filled with feed, the second valve 644 can be opened andthe first valve 642 can be closed near the end of the desorbing cycle.The desorbent can push the feed in the second pipe volume 630 into therotary valve 300 and displace the desorbent in the first line 422. Thus,the feed entering the first line 422 at the beginning of the next feedcycle can push the preloaded feed into the second bed 240. Consequently,the second pipe volume 630 may then be filled with desorbent and whenthe desorb cycle starts again, the feed can then be allowed back intothe second pipe volume 630 to displace the desorbent into the pipe 632.

With respect to the output 520, the raffinate stream 524 and extractstream 528 can be used to fill respective third and fourth pipe volumes650 and 670 at the beginning of the cycle. As an example, if theraffinate is exiting the first bed 230, the raffinate can pass throughthe second line 416, pass the check valve 418 to the rotary valve 300.However at the beginning of the cycle, the second line 416 can be filledwith extract from the previous cycle. As a consequence, the first valve662 can be closed and the second valve 664 can be opened allowing theraffinate to push the extract remnant in the second line 416 through therotary valve 300 through the pipe 652 into the third pipe volume 650.Initially, the third pipe volume 650 can be filled with raffinate fromthe previous cycle. The extract entering the third pipe volume 650 canpush the raffinate into the pipe 652 downstream of the valve 662. Oncethe third pipe volume 650 is filled with extract, the first valve 662can open and the second valve 664 can close. At this point, the firstand second control valves 654 and 656 can throttle to allow theraffinate in the pipe 652 to push the extract remnant in the third pipevolume 650 past the second control valve 656 where the extract can bewithdrawn and combined with the extract stream 528. Once the third pipevolume 650 is cleared of the extract and filled with raffinate, thesecond control valve 656 can close, and the first control valve 654 canremain open and the raffinate can proceed to the raffinate stream 524.Hence, the third pipe volume 650 is now filled with raffinate at thebeginning of the next raffinate cycle.

Similarly, if the extract is being withdrawn from the third bed 250, theprevious cycle would have raffinate in the second line 436. Withdrawingthe extract from the third bed 250 can dislodge the raffinate in thesecond line 436 that passes through the check valve 438 and the rotaryvalve 300. The first valve 682 can close and the second valve 684 canopen to force the raffinate in the second line 436 to pass into thefourth pipe volume 670, which may be filled with extract from theprevious cycle. Next, the second valve 684 and first control valve 674can be opened and the first valve 682 and the second control valve 676can be closed so the raffinate will dislodge the extract in the fourthpipe volume 670 and push it past the second valve 684 and out to theextract stream 528. Once the fourth pipe volume 670 fills with raffinatefrom the second line 436, the first valve 682 can open and the secondvalve 684 can close. The first and second control valves 674 and 676 canthrottle to allow the extract now passing through the pipe 672 to pushthe raffinate in the fourth pipe volume 670 past the second controlvalve 676 to the raffinate stream 524. Once the fourth pipe volume 670is cleared of the raffinate, the second control valve 676 can close andthe first control valve 674 can remain open so that the extract canleave the system through the pipe 672 and exit via the extract stream528. Hence, the fourth pipe volume 670 can be filled with extract forthe next cycle.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A method of minimizing cross-contamination of fluids in a simulatedmoving bed, comprising: A) filling a replacement volume on one side of avalve corresponding to a volume in a line on the other side of the valveto either dislodge a remnant in the line from a previous input, orreceive a remnant in the line from a previous output wherein theprevious input or output is different from the current input or output.2. The method according to claim 1, wherein the method dislodges theremnant from a previous input of a feed or a desorbent.
 3. The methodaccording to claim 1, wherein the method receives the remnant from anoutput of a raffinate or an extract.